Voltage regulator having a constant current controlled, constant voltage reference device

ABSTRACT

A feedback loop, including a low beta transistor and a second transistor with the bases connected to the collectors to form a loop, is utilized to provide a flow of current to a zener diode to maintain a reference voltage thereacross. The feedback loop is so arranged that said current is substantially constant in normal operation and is virtually independent of the supply voltage applied to the circuit.

United States Patent 1191 1111 3,881,150 Gay Apr. 29, 1975 VOLTAGEREGULATOR HAVING A 3.522.521 8/1970 Lloyd 323/22 T CONSTANT CURRENTCONTROLLED, 3,527,999 9/1970 Weinberger... 323/22 T 3.633.052 1/1972Hanna 307/299 B CONSTANT VOLTAGE REFERENCE 3.742.338 6/l973 Sugano et al323/22 T DEVICE 3.754.182 8/1973 Morris et al 323/22 T x Inventor:Michael John Gay, Scottsdale. Ariz.

Assignee: Motorola, Inc., Franklin Park, Ill.

Filed: Nov. 12, 1973 Appl. No.1 415,251

Related US. Application Data Continuation of Ser. No. 308,221. Nov. 20.l972, abandoned.

US. Cl. 323/22 T; 307/297; 307/299 B; 322/22 Z; 323/38 Int. Cl. G05f1/56 Field of Search 323/22 T, 22 Z. 34, 36, 323/38, 4, 9, 16; 307/299B, 297, 296

References Cited UNITED STATES PATENTS 8/1965 Kuriger 323/22 T PrimaryExaminer-Gerald Goldberg Almrney. Agent, or Firm-Vincent J. Rauner;Maurice J. Jones Jr.; Michael D. Bingham ABSTRACT 13 Claims, 1 DrawingFigure Ill/PU T /6 L040 (ammo/124m?) VOLTAGE l7 VOLTAGE REGULATOR HAVINGA CONSTANT CURRENT CONTROLLED, CONSTANT VOLTAGE REFERENCE DEVICE This isa continuation of application Ser. No. 308,221, filed Nov. 20, 1972, nowabandoned.

BACKGROUND OF THE INVENTION The present invention pertains to voltageregulators adapted to receive an unregulated voltage input and produce aregulated voltage output irrespective of impedance changes in loadoutput. Voltage regulators are utilized throughout the electronicindustry and are well known in a great variety of configurations withvarying complexities. In many high volume commercial applications it isimperative that the voltage regulator be constructed as simply andinexpensively as possible so that the structure in which it is utilizedcan be competitively priced. In a great many of these circuits zenerdiodes are utilized to provide a reference voltage. However, it is wellknown that a zener diode must be biased above a certain minimum currentto remove certain forms of noise signal. In general this current issufficiently high to cause significant voltage drop across parasiticseries resistances associated with the diode so that if the currentvaries substantially with the unregulated voltage applied to thecircuit, or the load, the regulation is seriously impaired.

SUMMARY OF THE INVENTION The present invention pertains to an improvedvoltage regulator utilizing a reference device, such as a zener diode,and a feedback loop including a low beta semiconductor device whichprovides substantially constant current to the reference device duringnormal operation to maintain a reference voltage thereacross. Thefeedback loop is so arranged that the current to the zener diode isvirtually independent of the supply voltage applied to the circuit.

It is an object of the present invention to provide an improved voltageregulator.

It is a further object of the present invention to provide an improvedvoltage regulator incorporating a feedback loop for providing currentto.a zener diode to maintain a reference voltage across the zener diode.

It is a further object of the present invention to provide an improvedvoltage regulator incorporating a zener diode and a feedback loopproviding to the zener diode a bias current which is reasonably wellcontrolled and is substantially independent of the unregulated inputvoltage and the load current, so that said bias current can be set abovethe level needed to ensure low noise without incurring poor regulation.

These and other objects of this invention will become apparent to thoseskilled in the art upon consideration of the accompanying specification,claims and drawing.

BRIEFDESCRIPTION OF THE DRAWING The single FIGURE is a schematic diagramof an embodimentof the improved voltage regulator.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGURE, thenumerals l and 11 designate a pair of input terminals adapted to beconnected to an unregulated voltage with the terminal being positive inthe present embodiment and the terminal 11 being a common. One end of aresistor 12 is connected to the terminal 10 and the other end isconnected to one end of a reference device, which in the presentembodiment is the cathode of a zener diode 13, the other end or anode ofwhich is connected to the common terminal 11. The cathode of the zenerdiode 13 is also connected to the base of an NPN type transistor, thecollector of which is connected to the terminal 10. The emitter of thetransistor 15 is connected to a junction 16 forming a portion of afeedback loop generally designated 17. The feedback loop 17 includes alow beta semiconductor device, which in this embodiment is a lateralconstruction type PNP transistor with a split collector ring, designated18, and also includes an NPN type transistor 19. Part of the collectorof the transistor 18 is connected to the base of the transistor 18(which connection may be formed internally when the device isconstructed if desired) and part of the collector is connected throughthe junction 16 to the base of the transistor 19. The collector of thetransistor 19 is connected to the base of the transistor 18 to form afeedback loop. The junction 16 is also connected to one side of areference device, which in this embodiment is the cathode of azenerdiode 20, the opposite side or anode being connected to the common 11.

The emitter of the transistor 18 is connected to the terminal 10. Theemitter of the transistor 19 is connected to the base of an NPN typetransistor 25. The transistor 25 is connected as a series passtransistor with the collector connected to the terminal 10 and theemitter connected to one side of a load 26, the other side of which isconnected to the common 11. A resistor 27 is connected between theemitter of the transistor 19 the side of the load 26 connected to theemitter of transistor 25. While specific types of components asemiconductor devices have been disclosed for exemplar purposes, itshould be understood that a variety of components and devices might beutilized by those skilled in the art.

In the operation of the above described circuit, when a sufficientlyhigh voltage is applied between the terminals 10 and 11 the transistor15 begins to conduct supplying base current to the transistor 19, whichalso begins to conduct. Conduction of the transistor 19 provides a basecurrent path for the transistor 18 which, upon conduction, conductscurrent from the terminal 10 to the base of the transistor 19. Thecurrent through the transistor 18 adds to the current throughthetransistor 15 and, assuming that the gain of the feedback loop 17 isgreater than unity, current in the loop 17 will regeneratively increase.Emitter current from the transistor l9 flows through the resistor 27 andthe load 26 to the common 11. The current supplied by transistor 19would increase until the voltage developed across the load, togetherwith that across the resistor 27, and that across the base emitterjunction of transistor 19, became sufficient to cause the zener diode 20to enter conduction, thereby reducing the loop gain of the circuit tobelow unity and preventing further regeneration. It is intended,however, that before the current supplied by transistor 19 reaches thislevel the voltage across resistor 27 will reach such a level as to causetransistor 25 to enter conduction. Once this occurs further increases inload current are substantially supplied by transistor 25 so thattransistor 19 passes a substantially constant current defined by thebase emitter voltage of transistor 25 and the resistor 27. Since thiscurrent is supplied to the base of the transistor 18 it causes asubstantially constant current to be supplied by transistor 18 to thejunction 16 of the zener-diode and the base of transistor 19. The basecurrent required by transistor 19 is readily made insignificant so thatthe current supplied by transistor 18 is virtually all passed by thezener diode 20. The current passed by the zener diode is thus determinedby the base emitter voltage of transistor 25 the value of resistor 27and the current gain of transistor 18. In order that this current bewell 'defined the current gain of transistor 18 must be well controlled.This control is most easily achieved by setting the gain to a low value,for example by using the well known twin collector lateral PNPconstruction connected as in the circuit diagram shown. It is alsopreferable that transistor 18 have a low current gain inasmuch as thisallows the use of a lower value resistor, 27, for a given zener diodebias current and, thereby, ensures that the relatively constant current,defined by the base emitter voltage of transistor 25 applied across thisresistor, substantially exceeds the highly loaddependent base current ofsaid transistor.

it should be noted that the zener diode l3, resistor 12 and transistorserve only to provide a starter circuit to supply the initial basecurrent to transistor 19. The

zener diode 13 is chosen to have a zener breakdown voltage equal to orsomewhat lower than that of zener diode 20. Thus, at some point beforefull voltage is established across the zener diode the transistor 15will cease conduction due to an insufficiency of base emitter voltageand thereafter this part of the circuit has no further effect on theoperation.

Thus, a relatively simple voltage regulator has been described whichprovides an output voltage with a high degree of isolation fromfluctuations in the input voltage and which utilizes a substantiallyconstant control currentto maintain a reference voltage therein whichcurrent and, therefore, the reference voltage, are virtually independentof the supply voltage.

While I have shown and described a specific embodiment of thisinvention, further modifications and improvements will occur to thoseskilled in the art. I desire it to be understood, therefore, that thisinvention is not limited to the particular form shown and I intend inthe appended claims to cover all modifications which do not depart fromthe spirit and scope of this invention.

I claim:

1. A voltage regulator circuit responsive to an unregulated voltagedeveloped between first and second conductors to provide a regulatedvoltage between a third conductor and the second conductor, the voltageregulator circuit including:

a first reference device having a first electrode connected to thesecond conductor and a second electrode first electron control meanshaving a control electrode connected to the second electrode of saidfirst reference device, a first electrode and a second electrode;

second electron control means having a first electrode connected to thefirst conductor, a control electrode directly connected to said secondelectrode of said first electron control means, a second electrodeconnected directly to said second electrode of said first referencedevice, and a third electrode connected directly to said secondelectrode of said first electron control means; and

circuit means connecting said first electrode of said first electroncontrol means to the third conductor.

2. The voltage regulator circuit of claim 1 wherein said circuit meansincludes:

third electron control means having a control electrode connected tosaid first electrode of said first electron control means, a firstelectrode connected directly to the third conductor, and a secondelectrode connected directly to said first conductor; and

first resistive means connected directly between said control electrodeof said third electron control means and said third conductor.

3. A voltage regulator circuit responsive to an unregulated voltagedeveloped between first and second conductors to provide a regulatedvoltage between a third conductor and the second conductor, the voltageregulator circuit including:

a first reference device having a first electrode connected to thesecond conductor and a second electrode;

first electron control means having a control electrode connected to thesecond electrode of said first reference device, a first electrode and asecond electrode;

second electron control means having a first electrode connected to thefirstconductor, a control electrode connected to said second electrodeof said first electron control means, and a second electrode connectedto said second electrode of said first reference device;

circuit means connecting said first electrode of said first electroncontrol means to the third conductor; and

a starting circuit having fourth electron control means having a firstelectrode connected to said second electrode of said second electroncontrol means, a second electrode connected to the first conductor, acontrol electrode, a second reference device having a first electrodeconnected to said second conductor, a second electrode connected to saidcontrol electrode of said fourth electron control means, secondresistive means connected between said first conductor and said controlelec trode of said fourth electron control means.

4. The voltage regulator circuit of claim 3 wherein each of saidelectron control means include bipolar transistors having emitter, baseand collector elec trodes respectively forming said first, control andsecond electrodes and each of said reference devices includes a zenerdiode.

- 5. The voltage regulator circuit of claim 4 wherein said bipolartransistor included by said second electron control means has a lowbeta.

6. The voltage regulator circuit of claim 5 wherein said bipolartransistor means included by said second electron control means has twocollector electrodes, one of which is connected to the base thereof.

7. A voltage regulator circuit providing a regulated voltage betweenfirst and second terminals in response to an unregulated voltage appliedbetween first and third terminals including in combination:

first zener diode means having a first electrode connected to the firstterminal and a second electrode;

first resistive means connecting the second electrode of said firstzener diode means to the third terminal;

first transistor means having a base electrode connected to the secondelectrode of said first zener diode means, a second electrode connectedto the third terminal and a first electrode at which a starting currentis developed;

second transistor means having a first electrode connected to the thirdterminal, a second electrode connected to the first electrode of thefirst transistor means, and a base electrode;

third transistor means having a first electrode, a base electrodeconnected to said second electrode of said second transistor means, asecond electrode connected to said base electrode of said secondtransistor means; second zener diode means having -a first electrodeconnected to said base of said third transistor means and a secondelectrode connected to the first terminal; and

circuit means connecting said first electrode of said thirdtransistormeans to the second terminal.

8. The voltage regulator circuit of claim 7 wherein said circuit meansincludes:

pass transistor means having a base electrode connected to said firstelectrode of said third transistor means, a first electrode connected tothe second terminal, and a second electrode connected to the thirdterminal.

9. The voltage regulator circuit of claim 8 further including secondresistive means connected between the second terminal and said baseelectrode of said pass transistor means.

10. In a voltage regulator circuit for use in an integrated circuitwhich provides aregulated voltage between first and second conductors inresponse to an unregulated voltage between first and third conductorscomprising first reference means having a first electrode connected tothe first conductor and a second electrode, and first electron controlmeans having a control electrode connected to the second electrode ofthe first reference means, a first electrode coupled to the secondconductor and a second electrode, wherein the improvement comprises:

second electron control means having a low beta and a control electrodeconnected to the second electrode of the first electron control means, afirst electrode connected to the third conductor and a second electrodeconnected to the second electrode of the first reference means and tothe control electrode of the first reference means and to the controlelectrode of the first electron control means;

third electron control means having a first electrode connected to thesecond conductor, a control electrode connected to a first electrode ofthe first electron control means and a second electrode connected to thethird conductor; and

first resistive means connected between said control electrode of saidthird electron control means and the second conductor.

11. The combination of claim 10 further including a starting circuithaving:

fourth electron control means with a first electrode connected to thesecond electrode of the first reference means and a second electrodeconnected to the third conductor and a control electrode coupled to thethird conductor; and

second reference means having a first electrode connected to saidcontrol electrode of said fourth electron control means and a secondelectrode connected to the first conductor.

12. The combination of claim 11 further including second resistive meansconnected between said control electrode of said fourth electron controlmeans and the third conductor.

13. The combination of claim 12 wherein said electron control means aresemiconductor transistors and said reference means are zener diodes.

1. A voltage regulator circuit responsive to an unregulated voltagedeveloped between first and second conductors to provide a regulatedvoltage between a third conductor and the second conductor, the voltageregulator circuit including: a first reference device having a firstelectrode connected to the second conductor and a second electrode;first electron control means having a control electrode connected to thesecond electrode of said first reference device, a first electrode and asecond electrode; second electron control means having a first electrodeconnected to the first conductor, a control electrode directly connectedto said second electrode of said first electron control means, a secondelectrode connected directly to said second electrode of said firstreference device, and a third electrode connected directly to saidsecond electrode of said first electron control means; and circuit meansconnecting said first electrode of said first electron control means tothe third conductor.
 2. The voltage regulator circuit of claim 1 whereinsaid circuit means includes: third electron control means having acontrol electrode connected to said first electrode of said firstelectron control means, a first electrode connected directly to thethird conductor, and a second electrode connected directly to said firstconductor; and first resistive means connected directly between saidcontrol electrode of said third electron control means and said thirdconductor.
 3. A voltage regulator circuit responsive to an unregulatedvoltage developed between first and second conductors to provide aregulated voltage between a third conductor and the second conductor,the voltage regulator circuit including: a first reference device havinga first electrode connected to the second conductor and a secondelectrode; first electron control means having a control electrodeconnected to the second electrode of said first reference device, afirst electrode and a second electrode; second electron control meanshaving a first electrode connected to the first conductor, a controlelectrode connected to said second electrode of said first electroncontrol means, and a second electrode connected to said second electrodeof said first reference device; circuit means connecting said firstelectrode of said first electron control means to the third conductor;and a starting circuit having fourth electron control means having afirst electrode connected to said second electrode of said secondelectron control means, a second electrode connected to the firstconductor, a control electrode, a second reference device having a firstelectrode connected to said second conductor, a second electrodeconnected to said control electrode of said fourth electron controlmeans, second resistive means connected between said first conductor andsaid control electrode of said fourth electron control means.
 4. Thevoltage regulator circuit of claim 3 wherein each of said electroncontrol means include bipolar transistors having emitter, base andcollector electrodes respectively forming said first, control and secondelectrodes and each of said reference devices includes a zener diode. 5.The voltage regulator circuit of claim 4 wherein said bipolar transistorincluded by said second electron control means has a low beta.
 6. Thevoltage regulator circuit of claim 5 wherein said bipolar transistormeans included by said second electron control means has two collectorelectrodes, one of which is connected to the base thereof.
 7. A voltageregulator circuit providing a regulated voltage between first and secondterminals in response to an unregulated voltage applied between firstand third terminals including in combination: first zener diode meanshaving a first electrode connected to the first terminal and a secondelectrode; first resistive means connecting the second electrode of saidfirst zener diode means to the third terminal; first transistor meanshaving a base electrode connected to the second electrode of said firstzener diode means, a second electrode connected to the third terminaland a first electrode at which a starting current is developed; secondtransistor means having a first electrode connected to the thirdterminal, a second electrode connected to the first electrode of thefirst transistor means, and a base electrode; third transistor meanshaving a first electrode, a base electrode connected to said secondelectrode of said second transistor means, a second electrode connectedto said base electrode of said second transistor means; second zenerdiode means having a first electrode connected to said base of saidthird transistor means and a second electrode connected to the firstterminal; and circuit means connecting said first electrode of saidthird transistor means to the second terminal.
 8. The voltage regulatorcircuit of claim 7 wherein said circuit means includes: pass transistormeans having a base electrode connected to said first electrode of saidthird transistor means, a first electrode connected to the secondterminal, and a second electrode connected to the third terminal.
 9. Thevoltage regulator circuit of claim 8 further including second resistivemeans connected between the second terminal and said base electrode ofsaid pass transistor means.
 10. In a voltage regulator circuit for usein an integrated circuit which provides a regulated voltage betweenfirst and second conductors in response to an unregulated voltagebetween first and third conductors comprising first reference meanshaving a first electrode connected to the first cOnductor and a secondelectrode, and first electron control means having a control electrodeconnected to the second electrode of the first reference means, a firstelectrode coupled to the second conductor and a second electrode,wherein the improvement comprises: second electron control means havinga low beta and a control electrode connected to the second electrode ofthe first electron control means, a first electrode connected to thethird conductor and a second electrode connected to the second electrodeof the first reference means and to the control electrode of the firstreference means and to the control electrode of the first electroncontrol means; third electron control means having a first electrodeconnected to the second conductor, a control electrode connected to afirst electrode of the first electron control means and a secondelectrode connected to the third conductor; and first resistive meansconnected between said control electrode of said third electron controlmeans and the second conductor.
 11. The combination of claim 10 furtherincluding a starting circuit having: fourth electron control means witha first electrode connected to the second electrode of the firstreference means and a second electrode connected to the third conductorand a control electrode coupled to the third conductor; and secondreference means having a first electrode connected to said controlelectrode of said fourth electron control means and a second electrodeconnected to the first conductor.
 12. The combination of claim 11further including second resistive means connected between said controlelectrode of said fourth electron control means and the third conductor.13. The combination of claim 12 wherein said electron control means aresemiconductor transistors and said reference means are zener diodes.